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Abstract:

An impact-modified polypropylene composite is made by mixing from 65 to
97 weight parts polypropylene having a glass transition temperature of
greater than -25° C., from 3 to 35 weight parts propylene-based
elastomer having a density of from 0.860 g/cc to 0.875 g/cc, a melting
point of from 130° C. to 170° C., a glass transition
temperature of from -35° C. to -25° C., and a melt flow
rate of from 3.0 to 15.0 g/10 minutes, and from 0.1 to 20 weight parts of
exfoliated silicate platelets.

Claims:

1. A composite made by mixing: from 65 to 97 weight parts polypropylene
having a glass transition temperature of greater than -25.degree. C. and
comprising one or more polymers selected from propylene homopolymer and
co-polypropylene; from 3 to 35 weight parts propylene-based elastomer
having a density of from 0.860 g/cc to 0.875 g/cc, a melting point of
from 130.degree. C. to 170.degree. C., a glass transition temperature of
from -35.degree. C. to -25.degree. C., and a melt flow rate of from 3.0
to 15.0 g/10 minutes, wherein the propylene-based elastomer comprises
ethylene/propylene/1-butene copolymer having a propylene monomer content
of from 55 to 90 mole %, an ethylene monomer content of from 4 to 25 mole
%, and a 1-butene monomer content of from 10 to 25 mole %; and from 0.1
to 20 weight parts of exfoliated silicate platelets having an average
size of less than 90 nm in at least one direction, wherein the total
weight of the polypropylene, the propylene-based elastomer, and the
exfoliated silicate platelets is 100 weight parts.

2. The composite of claim 1 wherein the propylene-based elastomer has a
density of from 0.865 to 0.870 g/cc.

3. The composite of claim 1 wherein the propylene-based elastomer has a
melting point of at least 135.degree. C.

4. The composite of claim 1 wherein the propylene-based elastomer has a
melting point of at most 160.degree. C.

5. The composite of claim 1 wherein the propylene-based elastomer has a
propylene monomer content of from 60 to 75 mole %.

6. The composite of claim 1 wherein the propylene-based elastomer has a
melt flow rate at least 5.0 g/10 minutes.

7. The composite of claim 1 wherein the propylene-based elastomer has a
melt flow rate of at most 8.0 g/10 minutes.

8. The composite of claim 1 wherein the propylene-based elastomer has a
glass transition temperature of at least -30.degree. C.

9. The composite of claim 1 made by mixing from 5 to 25 weight parts of
the propylene-based elastomer.

10. The composite of claim 1 comprising from 0.5 to 10 weight parts of
exfoliated silicate platelets having an average size of less than 90 nm
in at least one direction.

Description:

[0002] Composites of exfoliated clay particles dispersed in polypropylene
can increase the modulus (e.g., stiffness) relative to unfilled
semi-crystalline polypropylene. However, the brittleness of such
composites tends to increase, and the impact strength tends to decrease,
with particularly significant decrease at relatively cold temperatures
approaching the glass transition temperature of the polypropylene medium.

[0003] Elastomeric impact modifiers may be incorporated into polypropylene
to improve the impact strength performance by providing relatively "soft"
domains to dissipate impact energy. However, incorporation of impact
modifier tends to reduce the modulus of the resulting blend relative the
unmodified polypropylene. If exfoliated clay particles are incorporated
into traditionally impact-modified polypropylene, it is believed that the
exfoliated clay particles tend to partition preferentially into the more
compatible elastomeric impact modifier domains, which reduces the ability
of the particles to enhance modulus.

SUMMARY

[0004] One or more embodiments of the present invention may address one or
more of the aforementioned problems.

[0005] In an embodiment, a composite is made by mixing: [0006] from 65
to 97 weight parts polypropylene having a glass transition temperature of
greater than -25° C. and comprising one or more polymers selected
from propylene homopolymer and co-polypropylene; [0007] from 3 to 35
weight parts propylene-based elastomer having a density of from 0.860
g/cc to 0.875 g/cc, a melting point of from 130° C. to 170°
C., a glass transition temperature of from -35° C. to -25°
C., and a melt flow rate of from 3.0 to 15.0 g/10 minutes, wherein the
propylene-based elastomer comprises ethylene/propylene/1-butene copolymer
having a propylene monomer content of from 55 to 90 mole %, an ethylene
monomer content of from 4 to 25 mole %, and a 1-butene monomer content of
from 10 to 25 mole %; and [0008] from 0.1 to 20 weight parts of
exfoliated silicate platelets having an average size of less than 90 nm
in at least one direction, wherein the total weight of the polypropylene,
the propylene-based elastomer, and the exfoliated silicate platelets is
100 weight parts.

[0009] These and other objects, advantages, and features of various
embodiments of the invention will be more readily understood and
appreciated by reference to the detailed description.

DETAILED DESCRIPTION

[0010] Various embodiments of the present invention are directed to
composites comprising polypropylene, propylene-based elastomer, and
exfoliated silicate platelets, as described herein.

Polypropylene

[0011] The composite of the one or more embodiments may comprise from 65
to 97 weight parts of polypropylene, for example, polypropylene
comprising at least 90 mole % propylene monomer content and from 0 to 10
mole % of monomer content selected from ethylene monomer content and any
of C4 to C10 alpha-olefin monomer content. As used herein, the propylene
monomer content of a polymer refers to the amount of mer units of the
polymer derived from, or corresponding to, propylene. Likewise, ethylene
monomer content of a polymer refers to the amount of mer units of the
polymer derived from, or corresponding to, ethylene, and so on for the
other references to monomer content of a polymer.

[0012] The composite may comprise any of the polypropylenes described in
his section, and combinations thereof, in at least any of 65, 70, 75, 80,
85, 90, and 95 weight parts, and/or at most any of 97, 95, 90, 85, 80,
75, and 70 weight parts, and ranges between any of these amounts (e.g.,
from 70 to 95 weight parts). Unless specified otherwise, "weight parts"
as used herein is based on the total weight of the recited polypropylene,
the recited propylene-based elastomer, and the recited exfoliated
silicate particles herein in the composite equaling 100 weight parts.

[0013] The polypropylene may be a homopolymer polypropylene. The
homopolypropylene may be selected from one or more of any of the
isotactic form, syndiotactic form, or atactic form, or combinations
thereof.

[0014] The polypropylene may comprise a co-polypropylene comprising (in
addition to propylene monomer content) monomer content selected from
ethylene monomer content and any of C4 to C10 alpha-olefin
monomer content. For example, the co-polypropylene may comprise at least
any of 0.1, 0.5, 1, 1.5, 2, 3, 4, and 5 mole % monomer content, and/or at
most 10, 9.5, 9, 8, and 7 mole % monomer content, and any range between
any of this amounts, of any of ethylene monomer content and/or any of
C4 to C10 alpha-olefin monomer content, and combinations
thereof. The co-polypropylene may comprise random co-polypropylene and/or
block co-polypropylene. As used herein, "copolymer" (e.g.,
co-polypropylene) means a polymer derived from two or more types of
monomers, and includes terpolymers, etc., such that "co-polypropylene"
may include propylene polymer having more than two types of monomer
content.

[0015] The polypropylene may have a glass transition temperature of
greater than any of the following: -25° C., -20° C.,
-15° C., -10° C., -5° C., 0° C., 5°
C., and 10° C.; and/or at most any of the following: -20°
C., -15° C., -10° C., -5° C., 0° C.,
5° C., 10° C., 15° C., and 20° C. All
references to the glass transition temperature of a polymer in this
application refer to the characteristic temperature at which glassy or
amorphous polymers become flexible as determined by differential scanning
calorimetry (DSC) according to ASTM D 3418.

[0016] The polypropylene may have a melting point of at least any of
160° C. and 165° C.; and/or at most any of 170° C.
and 175° C. The polypropylene may have a density of at least any
of 0.890, 0.895, 0.900, 0.905 g/cc; and/or at most any of 0.910, 0.905,
0.900, and 0.985 g/cc.

[0037] The composite of the one or more embodiments may comprise from 3 to
35 weight parts of propylene-based elastomer having a density from 0.860
g/cc to 0.875 g/cc, a melting point of from 130° C. to 170°
C., and a glass transition temperature of from -35° C. to
-25° C.

[0038] The composite may comprise the propylene-based elastomer in at
least any of the following amounts: 3, 5, 7, 10, 12, 15, 20, 23, 25, 30,
and 32 weight parts; and/or in at most any of the following amounts: 35,
32, 30, 27, 25, 23, 20, 18, 15, 12, 10, and 5 weight parts; and
combinations thereof. As mentioned above, unless specified otherwise,
"weight parts" as used herein is based on the total weight of the recited
polypropylene, the recited propylene-based elastomer, and the recited
exfoliated silicate particles herein in the composite equaling 100 weight
parts.

[0039] The propylene-based elastomer of the composite may have a density
of at least any of the following: 0.860, 0.862, 0.865, 0.870, and 0.872
g/cc; and/or at most any of the following: 0.875, 0.872, 0.870, 0.867,
0.863 g/cc; and combinations thereof. All references to the density of a
polymer in this application are determined according to ASTM D1505.

[0040] The propylene-based elastomer of the composite may have a melting
point of at least any of the following: 130, 135, 140, 145, 150, 155,
160, and 165° C.; and/or at most any of the following 170, 165,
160, 155, 150, 155, 150, 145, 140, and 135° C., and combinations
thereof. All references to the melting point of a polymer in this
application refer to the melting peak temperature of the dominant melting
phase of the polymer as determined by differential scanning calorimetry
(DSC) according to ASTM D-3418.

[0041] The propylene-based elastomer of the composite may have a glass
transition temperature of at least any of the following: -35, -32, -30,
-28, and -27° C.; and/or at most any of the following: -25, -27,
-28, -30, -32, and -33° C.; and combinations thereof.

[0042] The propylene-based elastomer of the composite may have a melt flow
rate (MFR) of at least any of the following: 3.0, 3.5, 4.0, 4.5, 5.0,
5.5, 6.0, 6.5, and 7.0 g/10 minutes; and/or at most any of the following:
15.0, 14.0, 13.0, 12.0, 11.0, 10.0, 9.5, 9.0, and 8.5 g/10 minutes; and
combinations thereof. All references to the melt flow rate of a polymer
in this application refer to the melt flow rate taken at 230° C.
under a load of 2.16 kg, unless specified otherwise, measured according
to ASTM D-1238 (Condition 230/2.16; Procedure B).

[0043] The propylene-based elastomer of the composite may comprise
ethylene/propylene/1-butene copolymer having a propylene monomer content
of from 55 to 90 mole %, an ethylene monomer content of from 4 to 25 mole
%, and a 1-butene monomer content of from 10 to 25 mole %, based on the
total monomer content of the copolymer. The ethylene/propylene/1-butene
copolymer may have a propylene monomer content of at least any of 55, 58,
60, 62, and 65 mole %; and/or at most any of 90, 85, 83, 80, 78, and 75
mole %; an ethylene monomer content of at least any of 4, 6, 8, 10, 12,
14, 16, 18, and 20 mole %; and/or at most any of 25, 23, 20, 18, 17, 15,
10, and 8 mole %; and a 1-butene monomer content of at least any of 10,
12, 15, 18, 20, and 22 mole %; and/or at most any of 25, 23, 20, 18, 15,
and 12 mole %; and combinations thereof, based on the total monomer
content of the copolymer.

[0044] The propylene-based elastomer may comprise
ethylene/propylene/1-butene terpolymer having monomer content consisting
essentially of, or consisting of, propylene monomer content, ethylene
monomer content, and 1-butene monomer content, such that there may not be
any other unlisted monomer content.

[0045] Exemplary propylene-based elastomer consisting of
ethylene/propylene/1-butene copolymer is commercially available from
Mitsui Chemicals, Inc. under the Notio trade name and the PN-2060,
PN-2070, and PN3560 product designation numbers. The Notio
propylene-based elastomers are polymerized using metallocene catalyst,
and may be characterized as having crystalline block portions and
amorphous chain portions inserted into the crystalline block portions to
yield very small crystalline domains.

[0046] Notio PN-2070 propylene-based elastomer is an
ethylene/propylene/1-butene terpolymer believed to have a propylene
monomer content reported as 71 mole %, has been measured as having
propylene/ethylene/butene monomer contents of approximately 67 mole %/22
mole %/and 11 mole %, respectively, and has reported physical properties
of a melting point of 138° C., a density of 0.867 g/cc, a glass
transition temperature of -29° C., and a melt flow rate of 7.0
g/10 min.

[0047] Notio PN-2060 propylene-based elastomer is an
ethylene/propylene/1-butene terpolymer believed to have a propylene
monomer content reported as 79 mole %, has been measured as having
propylene/ethylene/butene monomer contents of approximately 82 mole %/5
mole %/and 13 mole %, respectively, and has reported physical properties
of a melting point of 155° C., a density of 0.868 g/cc, a glass
transition temperature of -28° C., and a melt flow rate of 6.0
g/10 min.

[0048] Notio PN-3560 propylene-based elastomer is an
ethylene/propylene/1-butene terpolymer that has been measured as having
propylene/ethylene/butene monomer contents of approximately 72 mole %/14
mole %/and 14 mole %, respectively, and believed to have physical
properties of a melting point of 158° C., a density of 0.866 g/cc,
and a melt flow rate of 6 g/10 min.

[0049] Useful polypropylene-based elastomer may be manufactured, for
example, by one or more of the methods set forth in U.S. Patent
Application Publication 2008/0023215 A1 and U.S. Pat. No. 7,488,789 B2,
each of which is incorporated herein in its entirety by this reference.

Exfoliated Silicate Platelets

[0050] The composite of the one or more embodiments may comprise from 0.1
to 20 weight parts of exfoliated silicate platelets having an average
size of less than 90 nm in at least one direction. The exfoliated
silicate platelets may be derived from intercalated layered silicate, as
described herein.

[0051] The exfoliated silicate platelets may have an average aspect ratio
(i.e., the ratio of the average largest dimension to the average smallest
dimension of the platelets) of from 10 to 30,000. Typically, the aspect
ratio for the silicate platelets exfoliated from an intercalated layered
silicate may be taken as the length (largest dimension) to the thickness
(smallest dimension) of the platelets.

[0052] Useful aspect ratios for the exfoliated silicate platelets include
at least any of the following values: 10; 20; 25; 200; 250; 1,000; 2,000;
3,000; and 5,000; and/or at most any of the following values: 25,000;
20,000; 15,000; 10,000; 5,000; 3,000; 2,000; 1,000; 250; 200; 25; and 20.
The exfoliated silicate platelets may have an average size in the
shortest dimension of at least any of the following values: 0.5 nm, 0.8
nm, 1 nm, 2, nm, 3 nm, 4 nm, and 5 nm; and/or at most any of the
following values: 90 nm, 60 nm, 30 nm, 20 nm, 10 nm, 8 nm, 5 nm, and 3
nm, as estimated from transmission electron microscope ("TEM") images.
The exfoliated silicate platelets may have an average dimension small
enough to maintain optical transparency of the composite in which the
particles are dispersed.

[0053] The amount of exfoliated silicate platelets in the composite may be
at least any of the following values 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5,
and 10 weight parts; and/or may be at most any of the following values:
20, 15, 10, 8, 6, 5, 4, 3, 2, and 1 weight parts. The weight of the
exfoliated silicate platelets includes intercalating agent that may be
sorbed to the silicate platelets. Exemplary intercalating agents are
discussed herein.

[0054] It is believed that the exfoliated silicate platelets result when
individual silicate layers of a layered silicate are no longer close
enough to interact significantly with the adjacent layers via ionic,
electrostatic, or van der Waals attractions or to form strongly
correlated systems due to the large aspect ratios of the platelets. An
exfoliated layered silicate has lost its registry and may be relatively
uniformly and randomly dispersed in a medium. It is believed that the
dispersion in a medium occurs when the interlayer spacing of the layered
silicate is at or greater than the average radius of gyration of the
molecules comprising the medium.

Other Components

[0055] The composite of the one or more embodiments may comprise other
components such as compatibilizer (e.g., dispersing aids) as discussed
herein. Such compatiblizers may be used to enhance exfoliation of the
intercalated layered silicate in the composite. Useful compatibilzers
include polymers modified (e.g., grafted or copolymerized) with
unsaturated carboxylic acid anhydride (i.e., anhydride-modified polymer)
to incorporate anhydride functionality, which promotes or enhances the
adhesion characteristics of the polymer. Examples of unsaturated
carboxylic acid anhydrides include maleic anhydride, fumaric anhydride,
and unsaturated fused ring carboxylic acid anhydrides (e.g., as described
in U.S. Pat. No. 4,087,588, which is incorporated herein in its entirety
by reference). Examples of anhydride-modified polymers include the
anhydride-modified version of polyolefins such as polypropylene (e.g.,
propylene homo- and co-polymers), for example, maleic anhydride grafted
polypropylene available from DuPont under the FUSABOND M613 trade name.
Useful anhydride-modified polymers may contain anhydride moiety in an
amount (based on the weight of the modified polymer) of at least any of
the following: 0.1%, 0.5%, 1%, and 2%; and at most any of the following:
10%, 7.5%, 5%, and 4%.

[0056] Other useful additives include those known in the art of plastics,
such as antiblock agents, antioxidant agents, antislip agents, slip
agents, stabilizer agents, colorant agents, mold release agents, and
pigments.

[0061] Layered silicates comprise a plurality of silicate layers, that is,
a laminar structure having a plurality of stacked silicate sheets or
layers with a variable interlayer distance between the layers. The
average thickness of the silicate layers may be at least any of the
following: 3, 5, 8, 10, 15, 20, 30, 40, and 50 Å; and/or at most any
of the following: 60, 50, 45, 35, 25, 20, 15, 12, 10, 8, and 5 Å. For
example, many layered silicates have a silicate layer thickness ranging
from 8 to 11 Å. The average interlayer spacing of the layered
silicate at 60% relative humidity before intercalation with an
intercalating agent may be at least any of the following: 1, 2, 3, 4, 5,
6, 8, and 10 Å; and/or may be at most any of the following: 20, 15,
10, 8, 6, 5, 3, and 2 Å. The average interlayer spacing (i.e., the
gallery spacing) of a layered silicate (including an intercalated layered
silicate) refers to the distance between the internal faces of the
non-exfoliated, adjacent layers of representative samples of the layered
silicate. The interlayer spacing may be calculated using standard powder
wide angle X-ray diffraction techniques generally accepted in the art in
combination with Bragg's law equation, as is known in the art.

[0063] To enhance the ability to exfoliate the layered silicate to render
exfoliated silicate platelets as described herein, the layered silicate
may be intercalated with intercalating agent, which is sorbed between the
silicate layers in an amount effective to provide an intercalated layered
silicate having an expanded average interlayer spacing between the
silicate layers, for example, an average interlayer spacing for the
intercalated layered silicate of at least 20 Å. Thus, an intercalated
layered silicate comprises intercalating agent sorbed between the
silicate layers of the layered silicate. The term "sorbed" in this
context means inclusion within the layered silicate (for example, by
adsorption and/or absorption) without covalent bonding. An intercalating
agent that is sorbed between silicate layers may be held to the
interlayer surface of a silicate layer by one or more of ionic
complexing, electrostatic complexing, chelation, hydrogen bonding,
ion-dipole interaction, dipole-dipole interaction, and van der Waals
forces.

[0064] Useful intercalating agents may comprise onium functionality, or
may be free of onium functionality, such that the intercalated layered
silicate may be essentially free of intercalating agent comprising onium
functionality (for example, to comply with food packaging laws or
regulations restricting food contact with certain agents).

[0069] The intercalated layered silicate (and/or the composite of one or
more embodiments herein) may be essentially free of intercalating agent
comprising onium functionality, for example, essentially free from a
compound selected from any or all of the onium compounds identified
herein (for example, to comply with food packaging laws or regulations
restricting food contact with certain agents).

[0086] Additional useful intercalating agents are disclosed in U.S. Pat.
No. 5,760,121 issued 2 Jun. 1998 to Beall et al, which is incorporated
herein in its entirety by reference.

[0087] The amount of intercalating agent sorbed in the intercalated
layered silicate per 100 weight parts layered silicate may be at least
and/or at most any of the following: 5, 10, 20, 30, 50, 70, 90, 110, 150,
200, and 300 weight parts. The average interlayer spacing between the
silicate layers of the intercalated layered silicate may be at least any
of the following: 20, 30, 40, 50, 60, 70, 80, and 90 Å; and/or may be
at most any of the following: 100, 90, 80, 70, 60, 50, 40, 30, 25 Å.
The amount of the intercalating agent sorbed between the silicate layers
may be effective to provide any of the forgoing average interlayer
spacing between the silicate layers. The measurement of the average
interlayer spacing of the intercalated layered silicate may be made at a
relative humidity of 60%.

[0088] Exemplary intercalated layered silicates are commercially
available, for example, from Southern Clay Products under the Cloisite
20A trade name, which is a montmorillonite layered silicate intercalated
with dimethyl didehydrogenated tallow quaternary ammonium; from AkzoNobel
under the Perkalite trade name, which are modified hydrotalcites
organically modified with, for example, fatty acid (e.g., Perkalite F100
and F100S); and from Nanocor, Inc. under the Nanomer trade name.

Manufacture of the Intercalated Layered Silicate

[0089] The intercalated layered silicate used in making embodiments of the
composite may be commercially procured, or may be manufactured. To make
an intercalated layered silicate, a layered silicate is mixed with the
intercalating agent to effect the inclusion (i.e., sorption) of the
intercalating agent in the interlayer space between the silicate layers
of the layered silicate. In doing so, the resulting intercalated layered
silicate may be rendered organophilic (i.e., hydrophobic) and show an
enhanced attraction to an organic medium. The inclusion of the
intercalating agent within the interlayer spaces between the silicate
layers of the layered silicate increases the interlayer spacing between
adjacent silicate layers. This may disrupt the tactoid structure of the
layered silicate to enhance the dispersibility of the intercalated
layered silicate in a medium.

[0090] Methods of making intercalated layered silicates are known in the
art, for example, see U.S. Patent Application Publication 2010-0040653 A1
published 18 Feb. 2010 to Becraft et al (Attorney Docket D43637),
previously incorporated herein by reference.

[0091] The intercalated layered silicate may be further treated (or the
layered silicate may be treated before intercalation to form the
intercalated layered silicate) to aid dispersion and/or exfoliation in a
medium and/or improve the strength of a resulting polymer/silicate
interface. For example, the intercalated layered silicate (or the layered
silicate before intercalation to form the intercalated layered silicate)
may be treated with a surfactant or reactive species to enhance
compatibility with the medium. With many layered silicates, the silicate
layers terminate with surface silanol functionality. It may be desirable
for greater compatibility with non-polar matrices to render these
surfaces more hydrophobic. One method to achieve this is to modify the
surface (e.g., react the functional groups present on the edges of the
silicate layers) with an organosilane reagent (e.g., silane coupling
agent) such as, n-octadecyldimethylchlorosilane,
n-octadecyldimethylmethoxysilane, trimethylchlorosilane,
hexamethyldisilazane, and the like.

[0092] The intercalated layered silicate may be further treated with a
compatibilizer to aid dispersion, such as a wax, polyolefin oligomer, or
polymer having polar groups. Exemplary compatibilizer waxes include
polyethylene wax, oxidized polyethylene wax, polyethylene vinyl acetate
wax, polyethylene acrylic acid wax, polypropylene wax, montan wax,
carnauba wax, candelilla wax, beeswax, and maleated waxes. Examples of
maleated wax include maleic anhydride modified olefin oligomer or
polymer, and maleic anhydride modified ethylene vinyl acetate oligomer or
polymer. An oligomer or polymer may be modified (e.g., grafted) with
unsaturated carboxylic acid anhydride (i.e., anhydride-modified oligomer)
to incorporate anhydride functionality, which promotes or enhances the
adhesion characteristics of the oligomer or polymer (i.e., promotes or
enhances the compatibility of the modified oligomer or polymer with the
intercalated layered silicate). Examples of unsaturated carboxylic acid
anhydrides include maleic anhydride, fumaric anhydride, and unsaturated
fused ring carboxylic acid anhydrides. Anhydride-modified polymer may be
made by grafting or copolymerization, as is known in the art. Useful
anhydride-modified oligomers or polymers may contain anhydride group in
an amount (based on the weight of the modified polymer) of at least any
of the following: 0.1%, 0.5%, 1%, and 2%; and/or at most any of the
following: 10%, 7.5%, 5%, and 4%.

[0093] The amount of compatibilizer present or used (e.g., any of one or
more of any of the compatibilizers described herein) may be at least any
of 10, 20, 30, 40, 60, 80, 100, and 120 weight parts; and/or at most any
of 140, 120, 100, 80, 60, 40, and 20 weight parts either relative to 100
weight parts of intercalated layered silicate used in making the
composite, or relative to 100 weight parts of exfoliated silicate
platelets having an average size of less than 90 nm in at least one
direction.

[0094] The composite may be substantially free of organosilane reagent
(e.g., silane coupling agent), or substantially free of compatibilizers,
such as one or more of any of those discussed above.

Manufacture and Use of the Composite

[0095] Embodiments of the composite may be made by mixing the intercalated
layered silicate with the medium of polypropylene, propylene-based
elastomer, and optional other components to effect mixture of the
components and exfoliation of the intercalated layered silicate into
exfoliated silicate platelets within the composite. The composite may be
made by known compounding methods, for example, by dry blending the
individual components and subsequently melt mixing, either directly in an
extruder used to make a finished article comprising the composite, or by
pre-melt mixing in a separate extruder (e.g., a Banbury mixer, a Haake
mixer, a Brabender internal mixer, a single-screw extruder, or a twin
screw extruder) to form the composite.

[0096] A masterbatch of the intercalated layered silicate (i.e., "silicate
masterbatch") may be pre-made comprising the intercalated layered
silicate mixed with one or more of the medium components (i.e.,
polypropylene, propylene-based elastomer, and/or other additives such as
compatibilizer) to at least partially disperse and exfoliate the
intercalated layered silicate into exfoliated silicate platelets. The
silicate masterbatch may then be mixed with the remaining medium
components of the composite to form the composite having the desired
relative amounts of components, and to complete the remaining amount of
exfoliation of the intercalated layered silicate, as needed.

[0097] The intercalated layered silicate (or the silicate masterbatch) may
be mixed with the medium comprising polypropylene and propylene-based
elastomer under conditions effective to exfoliate at least a portion of
the intercalated layered silicate into exfoliated silicate platelets
dispersed in the medium.

[0098] The effective conditions to exfoliate the intercalated layered
silicate may include the addition of mixing and/or shearing energy to the
mixture of the intercalated layered silicate and the medium comprising
polypropylene and propylene-based elastomer. The process variables for
exfoliating the intercalated layered silicate in the medium include time,
temperature, geometry of the mixing apparatus, and the shear rate, and
generally requires a balance of these variables, as is known to those of
skill in the art. The balancing of these variables may take into account
the desire to minimize the physical degradation or decomposition of the
medium and/or the intercalating agent, for example, by limiting the upper
temperature of the processing and/or the amount of time at a selected
temperature during processing.

[0099] An increase in temperature generally provides more thermal energy
to enhance exfoliation. A decrease in temperature may lower the viscosity
of the mixture while increasing the shear rate. An increase in shear rate
generally enhances exfoliation. Shear rates of at least any of the
following may be applied to the mixture of the intercalated layered
silicate in the medium: 1 sec-1, 10 sec-1, 50 sec1, 100
sec-1, and 300 sec-1.

[0100] Illustrative methods or systems for applying shear to effect
exfoliation of the intercalated layered silicate in the composite and to
mix the components of the composite include mechanical methods for
shearing a flowable mixture, such as the use of stirrers, blenders,
Banbury type mixers, Brabender type mixers, long continuous mixers,
injection molding machines, and extruders (single-screw and twin screw
extruders).

[0101] The effective exfoliation conditions may comprise raising the
temperature of the composite mixture, so that the mixture is thermally
processible at a reasonable rate in the mechanical system either before,
while, or after adding the intercalated layered silicate to composite
mixture. During processing, the mixture of the intercalated layered
silicate in the medium may be at a temperature, for example, of at least
and/or at most any of the following temperatures: 150° C.,
200° C., 240° C., 280° C., 300° C.,
320° C., 350° C., 380° C., and 400° C. The
amount of residence time that the mixture of the intercalated layered
silicate and the other composite medium may reside at any of these
temperatures may be at least and/or at most any of the following times:
2, 4, 5, 8, 10, 12, 15, and 20 minutes.

[0102] Thus, one or more embodiments of the composite may be made by
mixing: [0103] from 65 to 97 weight parts of polypropylene having a
glass transition temperature of greater than -25° C. comprising
one or more polymers selected from any of the propylene homopolymers and
co-polypropylenes described herein, for example, at least any of 65, 70,
75, 80, 85, 90, and 95 weight parts, and/or at most any of 97, 95, 90,
85, 80, 75, and 70 weight parts; [0104] from 3 to 35 weight parts, for
example, at least any of 3, 5, 7, 10, 12, 15, 20, 23, 25, 30, and 32
weight parts; and/or at most any of 35, 32, 30, 27, 25, 23, 20, 18, 15,
12, 10, and 5 weight parts, of propylene-based elastomer having any
combination of characteristics described herein relative the
propylene-based elastomer, for example, a density of from 0.860 g/cc to
0.875 g/cc, a melting point of from 130° C. to 170° C., and
a glass transition temperature of from -35° C. to -25° C.,
and a melt flow rate of from 3 to 15 g/10 minutes, wherein the
propylene-based elastomer comprises ethylene/propylene/1-butene copolymer
having a propylene monomer content of from 55 to 90 mole %, an ethylene
monomer content of from 4 to 25 mole %, and a 1-butene monomer content of
from 10 to 25 mole %; [0105] from 0.1 to 20 weight parts exfoliated
silicate particles having an average size of less than 90 nm in at least
one direction, for example, at least any of 0.1, 0.5, 1, 1.5, 2, 2.5, 3,
4, 5, and 10 weight parts; and/or at most any of 20, 15, 10, 8, 6, 5, 4,
3, 2, and 1 weight parts, where the total weight of the polypropylene,
the propylene-based elastomer, and the intercalated layered silicate is
100 weight parts; and [0106] optionally compatibilizer as discussed
herein.

[0107] The composition may have a modulus of at least any of 140,000;
160,000; and 180,000 psi; and/or at most 200,000 psi. As used herein,
modulus measurements refers to the modulus of elasticity (Young's
modulus) measured at 23° C. (73° F.) according to ASTM
D882.

[0108] The composition may have an impact strength of at least any of 0.3,
0.4, 0.5, 0.7, and 0.8 joules; and/or at most 1.5 joules. As used herein,
impact strength measurements refer to the energy to break the sample
measured at 4.4° C. (40° F.) according to ASTM D3763
(Dynatup).

[0109] It is believed that the use of the propylene-based elastomer
described herein as the impact modifier for the polypropylene medium of
the composite results in a composite mixture that does not take on a
structure in which relatively large domains or "islands" of the impact
modifier are distributed within the polypropylene medium. Rather, it is
believed that the impact modifier forms a "network" of helical crystals
portions having a size in the range of 10 nm to 50 nm joining to
amorphous regions of impact modifier, such that the resulting composite
mixture provides for relatively small domains of the impact modifier
distributed within the polypropylene medium. Although not being bound by
this theory, it is believed that as a result of the above-described
domain structures, the exfoliated silicate platelets distributed in the
medium of propylene and propylene-based impact modifiers are hindered
from preferentially residing in the small impact modifier domains, and
accordingly, the exfoliate silicate platelets reside to a greater extent
in the polypropylene dominated phases. By residing in the polypropylene
dominated phases, the exfoliated silicate platelets can contribute to an
increase in the modulus of the composite by enhancing the crystallinity
of the polypropylene domains, as opposed to being preferentially
incorporated in the impact modifier domains, where the exfoliated
silicate platelets would have less of an effect on modulus enhancement.

[0110] Molding operations known in the art may be used to form useful
fabricated articles or parts comprising one or more embodiments of the
composite disclosed herein, such operations including injection molding,
blow molding, and profile extrusion. Articles that may be formed
comprising one or more embodiments of the composite disclosed herein
include articles for packaging or storing food products (e.g., meats,
beverages), including, for example, any of bottles, cups, tubs, trays,
containers, and lids; articles for household or personal use, for
example, toys; articles for use in automobiles, airplanes, or other
vehicles; machinery, including housings for mechanical equipment such as
lawn mowers; furniture such as outdoor furniture (e.g., lawn furniture);
outdoor equipment such as shovels (e.g., snow shovels).

[0111] A package may comprise the composite disclosed herein, for example,
a packaged food having a food product packaged within the package
comprising the composite. Such a package may provide enhanced modulus
performance as well as enhanced impact strength even at lower
temperatures, for example, at refrigeration temperatures of from
0° C. to 5° C. commonly found in refrigerators, and also at
freezer temperatures of at most 0° C., where the packaged food may
be stored so that the package comprising the composite has a temperature
of at most 0° C. and the food product is "frozen."

EXAMPLES

[0112] The following examples are presented for the purpose of further
illustrating and explaining embodiments of the present invention and are
not to be taken as limiting in any regard. Unless otherwise indicated,
all parts and percentages are by weight.

[0113] In the examples and comparatives below, the following materials
were used: [0114] "IC-1" is an intercalated clay, namely, dimethyl
didehydrogenated tallow quaternary ammonium intercalated montmorillonite
available from Southern Clay Products under the CLOISITE 20A trade name.
The concentration of the intercalating agent was 95 meq/100 g clay (i.e.,
approximately 30 weight % intercalant). [0115] "PP-1" is polypropylene
homopolymer available from ExxonMobil Corporation under the trade name
grade PP4062E7, believed to have a density of 0.90 g/cc, a melt flow rate
of 3.4 g/10 minutes (230° C., 2.16 kg), and a melting point of
163° C. [0116] "Comp-1" is a compatibilizer consisting of maleic
anhydride grafted polypropylene available from DuPont under the FUSABOND
M613 trade name. [0117] "Mod-1" is an impact modifier, namely, a
propylene-based elastomer consisting of an ethylene/propylene/1-butene
terpolymer available from Mitsui Chemicals Corporation under the Notio
PN-2070 trade name, and having the physical properties described in the
propylene-based elastomer section above. [0118] "Mod-2" is an impact
modifier, namely, amorphous ethylene/propene/1-butene copolymer (propene
rich) believed to have a density of 0.87 g/cc, a glass transition
temperature of -33° C. available from Evonik Industries (formerly
Degussa) under the VESTOPLAST Grade 708 trade name. In reference to a
polymer, "amorphous" means no significant melt peak shown by DSC;
accordingly an amorphous polymer in essence lacks a melting point. [0119]
"Mod-3" is an impact modifier, namely, amorphous
ethylene/propene/1-butene copolymer (propene rich) believed to have 6 wt.
% ethylene monomer content, 66 wt. % propylene monomer content, and 28
wt. % 1-butene content, a glass transition temperature of -33° C.,
and a density of 0.87 g/cc available from Evonik Industries (formerly
Degussa) under the VESTOPLAST Grade 750 trade name. [0120] "Mod-4" is an
impact modifier, namely, ethylene/propene/1-butene copolymer believed to
have a glass transition temperature of from -32° C. to -33°
C., a melting point of 104° C., and an MFR (2.16 kg, 140°
C.) of 350 g/10 minutes available from Evonik Industries (formerly
Degussa) under the VESTOPLAST EP X 01 trade name. [0121] "Mod-5" is an
impact modifier, namely, ethylene/propene/1-butene copolymer believed to
have a glass transition temperature of -32° C., a melting point of
161° C., and an MFR (2.16 kg, 230° C.) of from 180 to 200
g/10 minutes available from Evonik Industries (formerly Degussa) under
the VESTOPLAST EP X 22 trade name. [0122] "Mod-6" is an impact modifier,
namely, ethylene/propene/1-butene copolymer (propene rich) believed to
have a glass transition temperature of from -33° C. to -32°
C., a melting point of 161° C., and an MFR (2.16 kg, 230°
C.) of 138 g/10 minutes available from Evonik Industries (formerly
Degussa) under the VESTOPLAST EP X 35 trade name.

[0123] Each of the following masterbatches (MB 1 through MB 6) were made
by mixing in a Haake internal mixer the following materials in the
amounts shown in Table 1 below: intercalated clay (IC-1), compatiblizer
(Comp-1), and each of the impact modifiers Mod-1 through Mod-8 as show in
Table 1 below. Also, a masterbatch (MB7) was made by mixing the
intercalated clay (IC-1), compatibilizer (Comp-1), and polypropylene
(PP-1) in the amounts shown below. Each masterbatch was mixed for 5
minutes at 100 rpm, with an initial temperature varying between 160 and
180° C., depending on the melt index of the major resin.

[0124] Example 1 was made as a 10 mil thick film as follows. The
masterbatch MB1, polypropylene PP-1, and additional amount of the impact
modifier Mod-1 were dry blended and added to the feed throat of a Haake
single screw extruder Rheomex 252 equipped with a Maddox mixer (L/D=24)
and four heat zones (150, 190, 200, and 200° C.). The resulting
mixture was extruded through a 6-inch coat hanger die onto a chilled roll
to produce a 10 mil nominal thickness film. The amount of combined
masterbatch, impact modifier, and polypropylene were such to produce an
Example 1 film having a composition of 2 wt. % IC-1, 2 wt. % Comp-1, 20
wt. % Mod-1, and 76 wt. % PP-1.

[0125] Examples 2 through 11 films were made as 10 mil nominal thickness
films in a manner similar to that of Example 1 film, but using amounts of
combined masterbatch (MB1), impact modifier (Mod-1), and polypropylene
(PP-1) to produce Examples 2 through 11 films having the final
compositions set forth in Table 2. Comparatives 1 through 10 were made as
10 mil nominal thickness films in a similar manner as Example 1 film, but
using amounts of combined masterbatch (MB1 through MB7 of the
corresponding type), and/or impact modifier (of the corresponding type),
and/or polypropylene (PP-1) to produce Comparative Films 1-10 having the
final compositions set forth in Table 2 below.

[0126] Discussing the test results shown in Table 2, Comparative 8 sample
having 10% impact modifier showed a 9.58 times increase in impact
strength relative to pure polypropylene without impact modifier. The
Comparative 7 sample having 20% impact modifier showed an 11.77 times
increase in impact strength relative to pure polypropylene without impact
modifier. As discussed in the Background section, it is expected that the
use of impact modifier increases the impact strength.

[0127] Also for the Comparative 8 sample, the use of 10% impact modifier
resulted in a modulus only 0.73 times the modulus of the pure
polypropylene without impact modifier. The Comparative 7 sample having
20% impact modifier showed an even higher detriment to the modulus,
having only 0.5 times the modulus of the pure polypropylene without
impact modifier. As discussed in the Background section, it is expected
that the use of impact modifier decreases the modulus.

[0128] The Comparative 6 sample having dispersed exfoliated clay particles
showed a 1.92 times increase in modulus relative to pure polypropylene
without dispersed exfoliated clay particles. However, the impact strength
of the Comparative 6 sample was only 0.38 times that of the pure
polypropylene sample without dispersed exfoliated clay particles. As
discussed in the Background section, it is expected that the dispersion
of exfoliated clay particles increases the modulus of polypropylene, yet
decreases the impact strength.

[0129] The Comparative 1-5 samples having both impact modifier and
dispersed exfoliated clay particles failed to show an improvement in both
the impact strength and the modulus relative the pure polypropylene.
Although the impact strength was enhanced for

[0130] Comparatives 1-2 and 4-5 (the normalized values were above 1), the
corresponding modulus failed to be enhanced (i.e., the normalized values
were at most 1.01). For Comparative 3, the impact strength decreased to
0.41 times that of pure polypropylene, although the modulus improved to
1.27 times that of pure polypropylene. Thus the Comparative 1-5 samples
failed to show improvement in both impact strength and modulus.

[0131] The Example 2-11 samples had impact modifier and dispersed
exfoliated clay particles in accordance with various embodiments of the
present invention. In contrast to the Comparatives, the Examples 2-9 and
11 showed enhancement of both the impact strength and the modulus
relative pure polypropylene. For example, Example 2 having 11% impact
modifier and 2% dispersed exfoliated clay particles had an impact
strength 3.77 times that of pure polypropylene and modulus 1.39 times
that of pure polypropylene. Example 11 having 20% impact modifier and
2.5% dispersed exfoliated clay particles had an impact strength 4.08
times that of pure polypropylene and modulus 1.11 times that of pure
polypropylene. Of the ten measured examples, only one (Example 10) failed
to show an improvement in both properties; and even Example 10 had a
improved impact strength 2.31 times that of pure polypropylene, but did
not show improvement in modulus (0.98 times that of pure polypropylene).

[0132] Thus, the vast majority of the Examples showed significant
improvements in both impact strength and modulus by the use of the
propylene-based elastomer of the recited type as impact modifier for
polypropylene in conjunction with exfoliated silicate particles in the
manner as disclosed herein. This is a surprising and unexpectedly good
result to one of skill in the art, as is seen by comparison to the
results of the Comparative samples, as discussed above.

[0133] One or more embodiments of the present invention are set forth
below in the following sentences A through W:

A. A composite made by mixing: [0134] from 65 to 97 weight parts
polypropylene having a glass transition temperature of greater than
-25° C. and comprising one or more polymers selected from
propylene homopolymer and co-polypropylene; [0135] from 3 to 35 weight
parts propylene-based elastomer having a density of from 0.860 g/cc to
0.875 g/cc, a melting point of from 130° C. to 170° C., a
glass transition temperature of from -35° C. to -25° C.,
and a melt flow rate of from 3.0 to 15.0 g/10 minutes, wherein the
propylene-based elastomer comprises ethylene/propylene/1-butene copolymer
having a propylene monomer content of from 55 to 90 mole %, an ethylene
monomer content of from 4 to 25 mole %, and a 1-butene monomer content of
from 10 to 25 mole %; and [0136] from 0.1 to 20 weight parts of
exfoliated silicate platelets having an average size of less than 90 nm
in at least one direction, wherein the total weight of the polypropylene,
the propylene-based elastomer, and the exfoliated silicate platelets is
100 weight parts. B. The composite of sentence A wherein the
propylene-based elastomer has a density of from at least any of the
following: 0.860, 0.862, 0.865, 0.870, and 0.872 g/cc; and/or at most any
of the following: 0.875, 0.872, 0.870, 0.867, 0.863 g/cc 0.865 to 0.870
g/cc. C. The composite of any one of the previous sentences wherein the
propylene-based elastomer has a melting point of at least any of the
following: 130, 135, 140, 145, 150, 155, 160, and 165° C.; and/or
at most any of the following 170, 165, 160, 155, 150, 155, 150, 145, 140,
and 135° C. D. The composite of any one of the previous sentences
wherein the propylene-based elastomer has a propylene monomer content of
at least any of 55, 58, 60, 62, and 65 mole %; and/or at most any of 90,
85, 83, 80, 78, and 75 mole %; and/or an ethylene monomer content of at
least any of 4, 6, 8, 10, 12, 14, 16, 18, and 20 mole %; and/or at most
any of 25, 23, 20, 18, 17, 15, 10, and 8 mole %; and/or a 1-butene
monomer content of at least any of 10, 12, 15, 18, 20, and 22 mole %;
and/or at most any of 25, 23, 20, 18, 15, and 12 mole %; and combinations
thereof, based on the total monomer content of the propylene-based
elastomer. E. The composite of any one of the previous sentences wherein
the propylene-based elastomer has a melt flow rate of at least any of the
following: 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, and 7.0 g/10 minutes;
and/or at most any of the following: 15.0, 14.0, 13.0, 12.0, 11.0, 10.0,
9.5, 9.0, and 8.5 g/10 minutes; and combinations thereof. F. The
composite of any one of the previous sentences wherein the
propylene-based elastomer has a glass transition temperature of at least
any of the following: -35, -32, -30, -28, and -27° C.; and/or at
most any of the following: -25, -27, -28, -30, -32, and -33° C.;
and combinations thereof. G. The composite of any one of the previous
sentences made by mixing from at least any of the following amounts: 3,
5, 7, 10, 12, 15, 20, 23, 25, 30, and 32 weight parts; and/or in at most
any of the following amounts: 35, 32, 30, 27, 25, 23, 20, 18, 15, 12, 10,
and 5 weight parts; and combinations thereof, of the propylene-based
elastomer. H. The composite of any one of the previous sentences wherein
the propylene-based elastomer consists of propylene monomer content,
ethylene monomer content, and 1-butene monomer content. I. The composite
of any one of the previous sentences comprising at least any of the
following amounts 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, and 10 weight parts;
and/or at most any of the following amounts: 20, 15, 10, 8, 6, 5, 4, 3,
2, and 1 weight parts of exfoliated silicate platelets having an average
size of less than at least any of 90 nm, or 60 nm, or 30 nm in at least
one direction. J. The composite of any one of the previous sentences
comprising at least any of 10, 20, 30, 40, 60, 80, 100, and 120 weight
parts; and/or at most any of 140, 120, 100, 80, 60, 40, and 20 weight
parts of compatibilizer relative to 100 weight parts of exfoliated
silicate platelets. K. The composite of any one of the previous sentences
wherein the polypropylene is a homopolymer. L. The composite of any one
of the sentences A through J wherein the polypropylene is a
co-polypropylene. M. The composite of sentence L wherein the
co-polypropylene comprises at least any of 0.1, 0.5, 1, 1.5, 2, 3, 4, and
5 mole % monomer content, and/or at most 10, 9.5, 9, 8, and 7 mole %
monomer content, and any combination thereof, of any of ethylene monomer
content and/or any of C4 to C10 alpha-olefin monomer content.
N. The composite of any one the previous sentences wherein the
polypropylene has a glass transition temperature of greater than any of
the following: -25° C., -20° C., -15° C.,
-10° C., -5° C., 0° C., 5° C., and 10°
C.; and/or at most any of the following: -20° C., -15° C.,
-10° C., -5° C., 0° C., 5° C., 10° C.,
15° C., and 20° C. O. The composite of one the previous
sentences made by mixing at least any of 65, 70, 75, 80, 85, 90, and 95
weight parts, and/or at most any of 97, 95, 90, 85, 80, 75, and 70 weight
parts of the polypropylene. P. The composite of any one of the previous
sentences wherein the composite is essentially free from intercalating
agent comprising any one of the functionalities selected from any of
onium functionality, ammonium functionality, phosponium functionality,
and/or arsonium functionality. Q. The composite of any one of the
previous sentences having an impact strength of at least any of 0.3, 0.4,
0.5, 0.7, and 0.8 joules; and/or at most 1.5 joules. R. The composite of
any one of the previous sentences having a modulus of at least any of
140,000; 160,000; and 180,000 psi; and/or at most 200,000 psi. S. A
packaged food comprising: [0137] a package comprising the composite of
any one of the previous sentences; and [0138] a food product packaged
within the package, wherein the package has a temperature of from
0° C. to 5° C. or at most 0° C. T. The packaged food
of sentence S wherein the package comprises a tray comprising the
composite of any one of the sentences A though R. U. A packaging article
comprising the composite of any one of the sentences A through R, wherein
the packaging article comprises one or more of any of bottles, cups,
tubs, trays, containers, and lids. V. An article comprising the composite
of any one of the sentences A through R, wherein the article is selected
from one or more of any of toys, automobiles, airplanes, vehicles,
housings for mechanical equipment, lawn mowers, furniture, outdoor
furniture, lawn furniture, shovels, snow shovels. W. A molded article
comprising the composite of any one of the sentences A through R.

[0139] Any numerical value ranges recited herein include all values from
the lower value to the upper value in increments of one unit provided
that there is a separation of at least 2 units between any lower value
and any higher value. As an example, if it is stated that the amount of a
component or a value of a process variable (e.g., temperature, pressure,
time) may range from any of 1 to 90, 20 to 80, or 30 to 70, or be any of
at least 1, 20, or 30 and/or at most 90, 80, or 70, then it is intended
that values such as 15 to 85, 22 to 68, 43 to 51, and 30 to 32, as well
as at least 15, at least 22, and at most 32, are expressly enumerated in
this specification. For values that are less than one, one unit is
considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are
only examples of what is specifically intended and all possible
combinations of numerical values between the lowest value and the highest
value enumerated are to be considered to be expressly stated in this
application in a similar manner.

[0140] The above descriptions are those of preferred embodiments of the
invention. Various alterations and changes can be made without departing
from the spirit and broader aspects of the invention as defined in the
claims, which are to be interpreted in accordance with the principles of
patent law, including the doctrine of equivalents. Except in the claims
and the specific examples, or where otherwise expressly indicated, all
numerical quantities in this description indicating amounts of material,
reaction conditions, use conditions, molecular weights, and/or number of
carbon atoms, and the like, are to be understood as modified by the word
"about" in describing the broadest scope of the invention. Any reference
to an item in the disclosure or to an element in the claim in the
singular using the articles "a," "an," "the," or "said" is not to be
construed as limiting the item or element to the singular unless
expressly so stated. The definitions and disclosures set forth in the
present Application control over any inconsistent definitions and
disclosures that may exist in an incorporated reference. All references
to ASTM tests are to the most recent, currently approved, and published
version of the ASTM test identified, as of the priority filing date of
this application. Each such published ASTM test method is incorporated
herein in its entirety by this reference.